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Proton electrochemical gradient and phosphate potential in submitochondrial particles.
Biochimica Et Biophysica Acta
|February 9, 1978
Summary
Mitochondrial ion uptake differs between inorganic and organic ions, impacting transmembrane potential and pH. Proton electrochemical potential (deltamuH) drives ATP synthesis, with inhibition occurring below 20 mV.
Area of Science:
- Biochemistry
- Mitochondrial Physiology
- Bioenergetics
Background:
- Submitochondrial particles exhibit differential ion uptake rates for inorganic versus organic ions.
- Transmembrane potential (deltapsi) and pH differential (deltapH) vary significantly based on ion type and concentration.
- Proton electrochemical potential difference (deltamuH) is a key indicator of mitochondrial energy status.
Purpose of the Study:
- To investigate the relationship between ion uptake, transmembrane potentials, and ATP synthesis in submitochondrial particles.
- To elucidate the role of proton electrochemical potential difference (deltamuH) in regulating ATP synthesis.
- To analyze the impact of weak bases and strong acids on mitochondrial bioenergetics.
Main Methods:
- Measurement of aerobic ion uptake by submitochondrial particles using radioactive tracers (e.g., 86Rb+, 125I-, acridines).
- Calculation of transmembrane pH differential (deltapH) and transmembrane membrane potential (deltapsi) based on ion distribution.
- Assessment of ATP synthesis rates under varying conditions of weak base and strong acid concentrations.
Main Results:
- Organic ions show significantly higher uptake than inorganic ions, correlating with larger deltapH and deltapsi values.
- Weak bases and strong acids modulate deltapH and deltapsi, with high concentrations decreasing overall proton electrochemical potential (deltamuH).
- ATP synthesis is inhibited only when deltamuH falls below 20 mV, indicating its critical role in energy production.
Conclusions:
- The type of ion influences the measured transmembrane potentials, highlighting the importance of ion selection in bioenergetic studies.
- Proton electrochemical potential difference (deltamuH) is the primary driver of ATP synthesis, and its decline leads to energy production inhibition.
- Mitochondrial function, specifically ATP synthesis, is robust but ultimately limited by the availability of proton electrochemical potential difference.